This invention relates to a lubrication system for an engine and, more particularly, to an improved lubrication system for lubricating the connection between the piston and the connecting rod of an engine in which the intake mixture is compressed at least, in part, in the crankcase chamber of the engine.
In two-cycle internal combustion engines and particularly those embodying crankcase compression principles, the engine is normally lubricated by delivering lubricant to the various components with the spent lubricant being passed out of the engine's exhaust system. This is done primarily because the crankcase chamber is not capable of functioning as a lubricant reservoir. Although this lubrication is frequently accomplished by mixing the lubricant with the fuel, such systems do not provide the optimum degree of lubricant for all running conditions. In addition, this type of systems requires fairly high oil concentrations in the fuel-air mixture to ensure that all components of the engine are adequately lubricated under high load conditions. Thus, these engines tend to consume a greater amount of oil than necessary for lubrication purposes at other running conditions and this oil enters the atmosphere through the exhaust.
There have also been provided systems wherein lubricant is added directly to the components to be lubricated from an external reservoir and wherein the lubricant is gradually depleted from this reservoir. Normally, the lubricant is directly delivered to the crankshaft bearings and to the sliding surfaces of the piston. However, the lubricant that is employed for lubricating the pivotal connection between the piston and piston pin and between the piston pin and connecting rod is normally accomplished by a mist-type system. Although some lubricant may be positively delivered in this area, generally the amount of lubricant required for these high stress surfaces is fairly high and, thus, smoke in the exhaust and other emission problems still are present.
It is, therefore, a principal object of this invention to provide an improved lubricating arrangement for the connection between the piston and connecting rod that will not require large amounts of lubricant.
It is further object of this invention to provide an improved method for lubricating the piston pin of an engine having crankcase compression and wherein the lubricating system is such that the oil is retained in the piston pin area so as to minimize the amount of lubricant that need be supplied.